Method for checking power status of batteries

ABSTRACT

A method of checking power status of the batteries is disclosed. New batteries are first prepared for discharge tests with different discharge rates, and the standard discharge data for different types of batteries are recorded in a data base for use in power estimation. Afterwards, the battery set installed in an uninterrupted power supply (UPS) system is connected to a monitoring device for continuous monitoring of the test discharge data and discharging time in repeated random discharge tests. The characteristic data including current output, operating temperature, and terminal voltage of the tested battery are then collected and compared with the relevant standard discharge data retrieved from the data base to produce a true estimation of the remaining power of the tested battery.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for checking the power status of batteries, in particular to a method that can considerably enhance the estimation of the remaining power of the tested battery.

[0003] 2. Description of Related Arts

[0004] The power for emergency power systems or uninterrupted power supply (UPS) systems generally comes from batteries. When the normal power supply is interrupted, the power source can be automatically switched to an emergency system that is capable of supplying the necessary power during the power outage. It is therefore very important to keep the emergency systems and the storage batteries in top operating conditions at all times. A number of techniques for checking the power status of these batteries have been discussed by prior art patents. One proposed a monitoring device for simultaneously monitoring of the battery characteristic data on several batteries on a continuous basis. These characteristic data include the current output, operating temperature, terminal voltage and remaining power. These characteristic data can be accurately measured with an appropriate means except the remaining power. Though important for a battery, the true power status of a battery at any given moment is hard to come by with acceptable confidence. FIG. 4 shows the relationship between the battery capacity and the amount of current output of a typical battery. Using a lead acid cell as an example, high current output of the battery generally results in small battery capacity in ampere/hour. In further analysis of the correlation between the two variables, it is found that the amount of current output of the battery is dependent on the electrolysis process of the electrode material with the electrolyte on the inner electrode plates of the battery. When the battery is in high discharge rate with a large current output, H₂SO₄ material will tend to accumulate in the gap between the electrode plates where the chemical reaction is taking place, causing the compound material to be changed to PbSO₄, thus blocking the infiltration of the compound material to the inner electrode plates, where no chemical reaction takes place. The battery capacity therefore is decreased drastically at a high discharge rate; on the contrary, when the battery is set to a low discharge rate with a small current output, H₂SO₄ is able to infiltrate to the inner electrode plates by capillary action to allow a complete chemical reaction on all electrode plates, thus the battery capacity is effectively increased. From the above experiment, it is known that the storage capacity of a battery tends to be inversely related to the amount of current output from a discharging battery.

[0005] However, even with the inverse relationship between the remaining power capacity and the current output, it is still difficult to come up with an acceptable method of checking the power status for any type of battery. The main problem is that different types of batteries exhibit different characteristics. There are so many types of batteries available, making it impossible to apply the above formula universally to estimate the remaining power capacity.

[0006] For a lead acid cell, as an example, the typical potential for chemical reaction is 2V, but the termination voltage will vary in accordance with the amount of current output and the type of battery used, which can be anywhere from 1.67V, 1.7V, 1.750V, 1.83V, to 1.9V. The following two cases fully demonstrate that different battery capacity will be produced for different amounts of current output and termination voltage.

[0007] Case 1: when the termination voltage is known to be 1.750V, a 2V 1000 A/h battery with a discharge rate of 100 A will be able to last for ten hours until the voltage eventually drops to 1.750V.

[0008] Case 2: when the termination voltage is known to be 1.832V, a 2V 1000 A/h battery with a discharge rate of 250 A will only last for three hours until the voltage eventually drops to 1.832V.

[0009] In both cases, even for two batteries with the same specifications and 100% battery capacity, the performance of the batteries will not be the same considering the variables such as the current output, battery makes, manufacturing process, and inherent quality, which will all be related to the termination voltage of a battery thus affecting their battery capacity. Also, temperature is another factor that may affect the battery capacity. The foregoing experiments only prove that it is grossly inadequate to make any estimation of the remaining power in a battery using a universal formula. Another prior art patent attempted to use the terminal voltage and the amount of current output to calculate the discharge rate, which is then multiplied by the amount of current output to generate the remaining power of a battery, but without considering the above mentioned factors that potentially will affect the battery capacity. It is apparent that this is a troublesome aspect for the maintenance of the storage batteries as they have to be kept in top condition at all times to meet the emergency needs.

SUMMARY OF THE INVENTION

[0010] The main object of the present invention is to provide a method for checking the power status of the storage batteries with accuracy and in a relatively short time.

[0011] The method comprising the steps of:

[0012] preparing new batteries of different types for discharge tests;

[0013] performing the discharge test on these new batteries for the first time to collect the standard discharge data and save them in a data base for subsequent use in battery tests;

[0014] performing random discharge tests on the UPS batteries to collect the discharge data in each operation cycle with a predetermined interval;

[0015] comparing and analyzing the discharge data of the tested batteries against the relevant standard discharge data from the data base; and

[0016] calculating the remaining power in the tested battery basing on the analysis results of the battery characteristic data.

[0017] The above mentioned method for checking the power status of a battery has to rely on the standard discharge data with respect to new batteries including their amount of current output and termination voltage. The standard discharge data for the same type of battery are selected from the data base for comparison with the discharge data from the tested battery.

[0018] The characteristic discharge data of the tested battery includes the terminal voltage, current output, and ambient temperature.

[0019] The features and structure of the present invention will be more clearly understood when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1 shows the logical steps for calculating the remaining power in a battery in accordance with the present invention;

[0021]FIG. 2 is a trending curve of battery capacity for a particular type of battery throughout its service life;

[0022]FIG. 3 is a comparative diagram of the storage capacities for different types of batteries; and

[0023]FIG. 4 shows typical characteristics of a conventional battery expressed in battery capacity C(%) and current output t(h).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024] The present invention provides a method for checking the power status of a battery, and the logical process is shown in FIG. 1 comprising the steps of:

[0025] determining when the battery discharge is started;

[0026] collecting the characteristic discharge data of the tested battery;

[0027] determining when the battery discharge is terminated;

[0028] comparing the collected discharge data with the relevant standard discharge data to calculate the remaining power of the tested battery;

[0029] determining whether the battery capacity of the tested battery is below the limit; and

[0030] issuing a warning message if the battery capacity is under the lower limit.

[0031] A description with respect to the logical steps mentioned above is given in more detail. To determine whether the battery is in the discharge mode, the tested battery is hooked up with a monitoring device, either fixed or portable, whilst a random discharge test is carried out on the tested battery on a continuous basis to determine when the battery is in the discharge mode. At the same time, the characteristic discharge data are collected in every cycle with a predetermined interval using a multi-channel monitoring device, which is able to monitor the discharging operation on several connected batteries simultaneously.

[0032] When the monitoring device detects that the tested battery is in the discharge mode, the device begins to collect the characteristic discharge data, including the terminal voltage, current output, and operating temperature, in each operation cycle with a predetermined interval.

[0033] The above characteristic data of the tested battery data is then used for calculating the remaining power therein, and the estimated power data for a particular battery will be saved in a battery power file. A trending curve depicting the distribution of remaining power for a particular battery throughout its service life is shown in FIG. 2. Upon request, this information can be provided to a user, along with a comparative chart of the battery capacity for various types of batteries as shown in FIG. 3. These standard discharge data will be helpful to the person responsible for keeping the storage battery in top operating conditions at all times.

[0034] Furthermore, a test-use data base is created for saving the characteristic data with respect to different types of batteries, which includes their termination voltage, current output and discharging time, along with other relevant data such as their specifications, battery makes, inherent quality, termination voltage, and current output.

[0035] When the monitoring device has collected the discharge data and the discharging time with respect to the tested battery, these data will be compared with the relevant standard discharge data retrieved from the data base, and an estimation of the remaining power will be calculated for the tested battery. Since the standard discharge data is obtained from a new battery using the same set of conditions, including the battery capacity, terminal voltage and current output, an estimation of the remaining power in the tested battery can be derived from the comparison of characteristic data between the test battery and the standard battery.

[0036] The comparison of battery characteristic data can be implemented in either one-to-several or several-to-several matching. For a one-to-several matching, the test computer makes the selection of a set of battery characteristic data from the data base having the same battery specifications as the tested batteries and uses it for comparison with the discharge data collected from the tested batteries. For a several-to-several matching, the computer selects more than one set of battery characteristic discharge data from the data base having the specifications matching against the respective tested batteries and use them for comparison with the discharge data collected from the tested batteries. The maximum number of data retrieval at one time is equal to the number of tested batteries connected to the monitoring device simultaneously. Specifically, each tested battery is matched against a set of standard discharge data from the data base, but the same set of standard discharge data may be shared by several tested batteries with similar specifications.

[0037] Furthermore, there is a positive correlation between the discharging time and the accuracy in power estimation. The accuracy is improved correspondingly with longer a period of discharging time. For a discharging time occupying more than 6% in a predetermined interval, the power estimation can be controlled to within a 10% discrepancy.

[0038] Besides the comparison and calculation of power estimation, the test computer is also responsible for checking whether the battery capacity of the tested battery is below the limit; if yes, it will issue a warning message calling for a check-up on the tested battery.

[0039] In summary, the present invention first creates a test data base containing the specifications, characteristic discharge data, and discharging time collected from different types of batteries which will be used as standard characteristic data for the new batteries. The discharging data of a tested battery is then collected in each operation cycle with a predetermined interval and compared with the relevant standard discharge data retrieved from the data base, basing on which a good estimation of the remaining power of the battery can be obtained as the conventional methods has largely ignored the battery capacity factor in their power estimation.

[0040] The foregoing description of the preferred embodiments of the present invention is intended to be illustrative only and, under no circumstances, should the scope of the present invention be so restricted. 

What is claimed is:
 1. A method for checking the power status of a battery comprising the steps of: determining when the battery discharge is started; collecting the characteristic discharge data and the discharging time of the tested battery; determining when the battery discharge is terminated; comparing the collected discharge data with the relevant standard discharge data to calculate the remaining power of the tested battery to be saved in a battery power file; wherein the standard discharge data is obtained from the first time discharging of a new battery for different types of batteries and all the standard data is saved in a data base for subsequent comparison with the test data from a tested battery.
 2. The method for checking the power status of a battery as claimed in claim 1, wherein the standard discharge data is selected by the test computer for comparison with discharge data from the tested batteries with one-to-several matching, that is to use one set of standard characteristic data to compare with the discharge data of several tested batteries having similar specifications.
 3. The method for checking the power status of a battery as claimed in claim 1, wherein the standard discharge data is selected by the test computer for comparison with discharge data from the tested batteries with several-to-several matching, that is to use multiple sets of standard characteristic data to compare with multiple sets of discharging data collected from their respective tested batteries having different specifications.
 4. The method for checking the power status of a battery as claimed in claim 2, wherein the maximum number of discharge data to be retrieved in one time for use in characteristic data comparison is equal to the number of battery cells simultaneously being connected.
 5. The method for checking the power status of a battery as claimed in claim 1, wherein after an estimation of the remaining power of a tested battery is produced a subsequent step checks whether the tested battery is below the lower storage capacity limit, and issues a warning message calling for battery check-up if the condition is met.
 6. The method for checking the power status of a battery as claimed in claim 1, wherein the estimated remaining power for different types of batteries contained in the battery power file can be used to produce a characteristic curve for the battery capacity and the type of battery used.
 7. The method for checking the power status of a battery as claimed in claim 1, wherein the power data contained in the battery power file can be used to construct a characteristic curve of the battery capacity distribution for a particular type of battery throughout the service life.
 8. The method for checking the power status of a battery as claimed in claim 1, wherein the battery characteristic data of a tested battery includes the terminal voltage, current output and operating temperature.
 9. The method for checking the power status of a battery as claimed in claim 1, wherein the discharging time of a tested battery occupies more than 6% of the predetermined testing period. 